WO2012009972A1

WO2012009972A1 - Key distribution method and system for handover

Info

Publication number: WO2012009972A1
Application number: PCT/CN2011/070533
Authority: WO
Inventors: 杜高鹏; 朱永升
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-07-22
Filing date: 2011-01-24
Publication date: 2012-01-26
Also published as: CN102340774A; CN102340774B

Abstract

A key distribution method and system for handover are provided in the present invention, the method includes the following steps: when a terminal switches between a source base station and a target base station, the target base station requests a key generation information from the core network; the target base station generates a key, which is used to derive a key of the access layer, based on the key generation information provided by the core network. The key distribution scheme provided in the present invention provides generation material of the key for the target evolved Node B (eNB) through Mobility Management Entity (MME), and the target eNB generates K_eNB key, in this way, in the X2 handover process, even if the source eNB is broken, the key K_eNB of the target eNB can not be got, therefore solving the security problem of the key distribution in the handover process, and achieving the purpose of one hop forward security.

Description

Switching key distribution method and system

Technical field

The present invention relates to the field of mobile communication technologies, and in particular, to a key distribution method and system for handover.

Background technique

With the popularity of mobile communications, security issues in mobile communications are receiving more and more attention, and higher requirements are placed on security in mobile communications. For the LTE (Long Term Evolution, Long Term Evolution) system, a terminal in LTE / S AE (System Architecture Evolution , System Architecture Evolution) mobile internal network, and LTE and other 3GPP (3 ^rd Generation Partnership Project, the Third Generation Partnership The problem of access security when the systems move with each other is the core key technology of LTE/SAE access security, and it is also the focus, hotspot and difficulty of current research of 3GPP SA3 (System and Business Working Group 3). It makes the process of moving EUTRAN (Evolved Universal Terrestrial Radio Access Network) products in the processing terminal more complicated, and may affect the performance of the wireless network in actual networking in the future, such as call drop rate, handover failure rate, etc. A major factor, therefore, the security issue in the mobile state has become the focus of attention of product line related units.

In the LTE system, when an X2 handover between two eNBs (evolved Node Bs) of the same MME (Mobile Management Entity) occurs, there is also a security problem of key distribution.

The current key distribution method is as follows: The first handover performs a horizontal key generation chain, and the subsequent handover performs a vertical key generation chain.

The prior art key distribution method will be described below with reference to the accompanying drawings. It is assumed that eNB A, eNB B, and eNB C belong to the same MME, and the UE performs X2 handover between three eNBs. FIG. 1 shows a schematic diagram of a key distribution process for the first handover. When eNB A switches to eNB B, eNB A performs a horizontal key generation chain. The specific process is described as follows:

Step 101: The UE reports a Measurement Report to the eNB A. Step 102: The eNB A makes a handover decision (HandOver Decision) according to the measurement report reported by the UE, and generates K _eNB *=KDF (K _eNB || PCI || EARFCN-DL);

The K _eNB is a shared key generated by the core network and sent to the eNB A when the UE accesses the eNB A, so that the eNB A derives the key of the AS (access layer) according to the key. KDF (Key Derivation Function) is a key derivation function.

Step 103, the eNB A initiates a Handover Request to the target base station eNB B, and forwards the {NCC, KeNB*} to the eNB B;

Among them, NCC (Next Hop Chaining Counter) is the next hop chain counter.

Step 104, eNB B makes K _eNB = K _eNB *;

Step 105, eNB B returns Handover Request Ack, and sets NCC

(At this time, NCC=0) is placed in the transparent container of the Handover Request Ack message;

Step 106, the eNB B sends a HO Command (Handover Command) to the UE, and sends the NCC (in this case, NCC=0) to the UE in a transparent container of the HO Command message;

Step 107, the UE generates K _eNB *,

II PCI II EARFCN_DL), and

Step 108: The UE sends a Handover Confirm to the eNB B.

Step 109: After completing the interaction with the handover signaling of the UE, the eNB B sends a Path Switch Request message to the MME.

Step 110: After receiving the Path Switch Request message, the MME should increment the locally saved NCC (previously NCC=1) value by 1, that is, let NCC=NCC+1; and calculate a new NH according to a function specified by the security parameter specification, NH= KDF (K _AS ME II NH Old), where K _ASME and locally stored NH values (NH_01d ) are used as inputs;

Step 111: The MME sends a newly calculated {NCC, NH} pair to the target eNB B in the Path Switch Ack message (in this case, NCC=2);

Step 112: The eNB B saves the received {NCC, NH} pair for the next switch, and deletes other {NCC, NH} pairs that may be existing but not used;

Step 113, after the handover is completed, the eNB B sends a Release Resource to the eNB A. The source message informs the eNB A to release the relevant resources of the UE.

FIG. 2 is a schematic diagram of a key distribution process for the first handover. Referring to FIG. 2, when the UE switches from eNB B to eNB C for the second time, eNB C performs a vertical key generation chain by using a new {NH, NCC}. .

Step 201: The UE sends a Measurement Report to the eNB B.

Step 202, eNB B makes a handover decision and generates K _eNB *, K _eNB * = KDF (NH | | PCI | | EARFCN DL);

Step 203: The eNB B forwards {NCC, K _eNB *} to the target eNB C through the Handover Request message (at this time, NCC=2);

Step 204, eNB C will K _eNB = K _eNB *;

Steps 205-206, the eNB C puts the NCC into the transparent container of the HO Command message, and forwards it to the UE through the source eNB B;

Step 207: The UE generates K _eNB * using the NH corresponding to the NCC in the message, that is, K _eNB *=KDF ( H II PCI || EARFCN_DL), and K _eNB = K _eNB *;

For the subsequent steps 208 ~ 213, refer to steps 108 ~ 113 in Figure 1. The main difference is that the NCCs of the two handovers are different, and will not be described here.

It can be seen from the above existing handover procedure that when the UE first switches from eNB A to eNB B, eNB A can derive the key of eNB B; when the UE switches from eNB B to eNB C for the second time, eNB B can The key of eNB C is derived. However, eNB A cannot calculate the key of eNB C, that is, it takes 2 hops to achieve the purpose of forward security. The term "forward security" refers to sharing a key K _eNB for one eNB and one UE, and the eNB cannot calculate a key between the UE and another eNB.

In summary, the key distribution of existing handovers has the following problems:

1. When the UE performs the X2 handover between the eNBs, the key K _eNB of the target eNB is provided by the source eNB, so that once the source eNB is compromised, the key K _{eNB of the} target eNB may be acquired during the X2 handover process. This is very unsafe; 2. The current key distribution mechanism requires at least 2 hops to achieve forward security purposes, and cannot reach ^\ 1 ϋ forward security. Summary of the invention

The technical problem to be solved by the present invention is to provide a method and system for key distribution of a handover, which can achieve the purpose of forward security for one hop.

In order to solve the above technical problem, the present invention provides a handover key distribution method, and the method includes:

When the terminal performs handover between the source base station and the target base station, the target base station requests key generation information from the core network;

The target base station generates a key according to the key generation information provided by the core network, and the key is used to derive the key of the access layer.

Optionally, the key generation information includes an intermediate key ( ΝΗ ) value corresponding to a next hop chain counter ( NCC );

In the step of the target base station generating a key according to the key generation information provided by the core network, the target base station generates a key K _eNB according to the threshold value.

Optionally, the step of the target base station requesting the key generation information from the core network includes:

When receiving the handover request sent by the source base station, the target base station generates a second NCC value according to the first NCC value included in the handover request, and sends a handover NCC request to the core network mobility management entity, where the handover NCC request includes the second NCC value;

When receiving the handover NCC request, the mobility management entity determines the NH value according to the second NCC value and the locally stored NCC value, and is included in the handover NCC response and sent to the target base station.

Optionally, the step of determining, by the mobility management entity, the NH value according to the second NCC value and the locally saved NCC value comprises:

The mobility management entity compares the second NCC value with the locally stored NCC value,

If the second NCC value is equal to the locally saved NCC value, determining the NH value corresponding to the second NCC value as the NH value; If the second NCC value is greater than the locally saved NCC value, the locally saved NCC value is set to the second NCC value, and the NH value corresponding to the second NCC value is calculated and determined as the NH value;

If the second NCC value is less than the locally saved NCC value, the locally saved NCC value is incremented. Optionally, the handover NCC response sent by the mobility management entity to the target base station further includes an NCC value corresponding to the NH value; the target base station receives The NCC value is saved and forwarded to the terminal;

The terminal calculates a corresponding NH value according to the NCC value sent by the target base station, and calculates K _eNB according to the calculated NH value.

Optionally, the target base station calculates the second NCC value according to the following formula:

NCC ₂ = I KDF(NCCi || K _eNB * || CRNTI), KDF(NCCi || K _eNB * || CRNTI)≠NCC max

KDF (NCCi II K _eNB * II CRNTI) -1 , KDF (NCCi || K _eNB * || CRNTI) = NCC maximum value, where NCd is the first NCC value, NCC ₂ is the second NCC value, and CRNTI is the cell Wireless network temporary identification.

Optionally, when the second NCC value is smaller than the NCC value saved by the mobility management entity, if the locally saved NCC value is equal to the maximum value in the NCC value range, the corresponding NCC value is directly calculated according to the locally saved NCC value. The NH value is determined as the NH value.

Optionally, the value range of the NCC is greater than or equal to 0 and less than or equal to 63.

Optionally, a switched key distribution system, the system includes: a base station and a core network, the base station includes a key information requesting unit and a key generating unit, and the core network includes a key information providing unit, wherein the key information requesting unit The method is configured to: when receiving a handover request requested by the terminal, requesting the key generation information from the core network;

The key information providing unit is configured to provide the key generation information for the key information request unit according to the request;

The key generation unit is configured to generate a key based on the key generation information provided by the key information providing unit, the key being used to derive a key of the access layer.

Optionally, the key generation information includes an NH value corresponding to the NCC, and the key generated by the key generation unit is a K _eNB ; The key information requesting unit is further configured to: generate a second NCC value according to the first NCC value included in the handover request, and request the key generation information from the core network by sending a handover NCC request to the core network mobility management entity, where the switching NCC is performed The request contains a second NCC value;

The key information providing unit is further configured to, when receiving the handover NCC request, determine the NH value according to the second NCC value and the locally stored NCC value, and include the transmission to the key information requesting unit in the handover NCC response.

Optionally, the key information providing unit is further configured to determine the NH value according to the second NCC value and the locally saved NCC value as follows:

Comparing the second NCC value with the locally saved NCC value,

If the second NCC value is equal to the locally saved NCC value, determining the NH value corresponding to the second NCC value as the NH value;

If the second NCC value is greater than the locally saved NCC value, the locally saved NCC value is set to the second NCC value, and the NH value corresponding to the second NCC value is calculated and determined as the NH value;

If the second NCC value is less than the locally saved NCC value, the locally saved NCC value is incremented.

Optionally, the system further includes a terminal, where the terminal further includes a key calculation unit,

The key information providing unit is further configured to further include, in the handover NCC response sent to the key information requesting unit, an NCC value corresponding to the determined NH value;

The key information requesting unit is further configured to: after receiving the NCC value, save and forward the data to the terminal; the key calculating unit is configured to calculate a corresponding NH value according to the NCC value sent by the received key information requesting unit, and calculate according to the calculation The resulting NH value is calculated as K _eNB .

The present invention also provides a base station in a key distribution system for handover, comprising a key information requesting unit and a key generating unit, wherein:

The key information requesting unit is configured to request key generation information from a core network in the switched key distribution system when receiving a handover request requested by the terminal;

The key generation unit is configured to: generate a key according to the key generation information provided by the core network according to the request of the key information request unit, where the key is used to derive the density of the access layer Key.

Optionally, the key generation information includes an intermediate key (NH) value corresponding to a next hop chain counter (NCC), and the key generated by the key generation unit is a K _eNB ;

The key information requesting unit is further configured to generate a second NCC value according to the first NCC value included in the handover request, and request key generation information from the core network by sending a handover NCC request to the core network mobility management entity. And including, in the handover NCC request, the second NCC value; and receiving a handover NCC response sent by the core network, where the handover NCC response includes the core network according to the second NCC value and a locally saved NCC The value of the determined NH value.

The present invention also provides a terminal in a switched key distribution system, comprising a key calculation unit, the key calculation unit being configured to be based on a next hop chain counter (NCC) transmitted by a base station in the switched key distribution system. The value calculates the corresponding intermediate key (NH) value, and calculates the key K _eNB based on the calculated NH value.

According to the key distribution scheme proposed by the present invention, the MME provides the target eNB with the generated material of the key, and the target eNB generates the K _eNB key. Thus, in the X2 handover process, even if the source eNB is compromised, the target cannot be acquired. The key K _{eNB of the eNB} solves the security problem of key distribution in the handover process and achieves the goal of 1 hop forward security. BRIEF abstract

The accompanying drawings are intended to provide a further explanation of the invention, and are a part of the description of the invention. Schematic diagram of the key distribution process for the first handover;

2 is a schematic diagram of a key distribution process of a second handover in the prior art;

FIG. 3 is a schematic diagram of a key distribution process of a handover according to an embodiment of the present invention.

Preferred embodiment of the invention

The core idea of the present invention is that, in the X2 handover, by the interaction between the target eNB and the MME, the MME provides the target eNB with the key generation material, and the target eNB performs the key generation. It is ensured that the source eNB cannot calculate the key between the target eNB and the UE, and achieves the goal of 1 hop forward security.

Based on the above idea, the present invention provides a handover key distribution method, which specifically uses the following technical solutions:

The target base station generates a key according to the key generation information provided by the core network, and the key is used to derive a key of the access layer.

Optionally, the key generation information includes an NH value corresponding to the NCC, and the key generated by the target base station according to the NH value is K _eNB .

Optionally, the requesting, by the target base station, the key generation information to the core network, the method includes: when the target base station receives the handover request sent by the source base station, generating, according to the first NCC value included in the handover request, generating a second An NCC value, and sending a handover NCC request to the core network mobility management entity, where the second NCC value is included in the handover NCC request;

When the mobility management entity receives the handover NCC request, it determines a corresponding NH value according to the second NCC value and the locally saved NCC value, and is sent to the target base station in the handover NCC response.

Optionally, the mobility management entity determines, according to the second NCC value and the locally saved NCC value, a corresponding NH value, specifically:

The mobility management entity compares the second NCC value with a locally saved NCC value, and if the second NCC value is equal to the locally saved NCC value, determining the NH value corresponding to the second NCC value as Said corresponding NH value;

If the second NCC value is greater than the locally saved NCC value, the locally saved NCC value is set to the second NCC value, and the NH value corresponding to the second NCC value is calculated and determined as the corresponding NH value;

If the second NCC value is smaller than the locally saved NCC value, the locally saved NCC value is incremented once, and the NH value corresponding to the incremented NCC value is calculated and determined as the corresponding value. Optionally, the value of the NCC is greater than or equal to 0 and less than or equal to 63.

KDF (NCCi II K _eNB * II CRNTI) -1 , KDF (NCCi || K _eNB * || CRNTI) = NCC maximum value, where NCCi is the first NCC value, NCC ₂ is the second NCC value, CRNTI (Cell Radio Network Temporary Identify) is the temporary identifier of the cell wireless network.

Optionally, when the second NCC value is less than the NCC value saved locally by the mobility management entity, if the locally saved NCC value is incremented to be equal to the maximum value in the NCC value range, the NCC is directly saved according to the local The value calculates the corresponding NH value and determines it as the corresponding NH value.

Optionally, the terminal calculates a corresponding NH value according to the NCC value sent by the target base station, and calculates K _eNB according to the calculated NH value.

The implementation of the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

FIG. 3 is a schematic flowchart of a key distribution method of a handover according to an embodiment of the present invention. As shown in FIG. 3, the process of this embodiment is specifically described as follows:

Step 301: The Measurement Report is performed on the UE;

Step 302: The source eNB makes a handover decision according to the Measurement Report reported by the UE, and generates a K _eNB *;

In this step, if it is the first switch, then ΝΒ ₆ ΝΒ* = KDF (K _ENB II PCI II

EARFCN DL); Otherwise, K _eNB * = KDF(NH || PCI || EARFCN- DL);

Step 303: The source eNB initiates a Handover Request to the target eNB, and forwards the {NCC, K _eNB *} to the target eNB through a Handover Request message.

Step 304: The target eNB generates an NCC*, NCC*=KDF (NCC || K _eNB * || CRNTI); preferably, in order to better secure the security of the key, the value range of the standard NCC in the present invention is [ 0, 7] to expand, if the value range can be taken as [0, 63], etc., so that the source eNB can be prevented from deriving the key of the target eNB according to the value of a limited number of NCCs. Further, preferably, if the NCC* generated by the target eNB in this step is the maximum value in the range, then NCC* = NCC*-1 is set to avoid the occurrence of the NCC flip.

Step 305: The target eNB sends a Handover NCC Request message to the MME, where the message carries the generated NCC*;

Step 306: After receiving the Handover NCC Request message, the MME compares the local NCC value with the NCC* value in the message, and determines the NH value as follows:

(i) If NCC* = NCC, the MME will NCC = NCC* and determine that the NH value is the NH corresponding to NCC;

(ii) If NCC* > NCC, the MME will NCC = NCC*, iteratively calculate the NH* corresponding to the NCC through the function defined by the security parameter specification, and then let NH = H*;

(iii) If NCC * < NCC , the MME will NCC = NCC + 1 , the purpose of which is to generate ΝΗ in the direction of increasing NCC.

In addition, for case (iii), in order to ensure that the NCC flip does not occur when using the vertical key generation method, that is, if the NCC value reaches the maximum value or the critical value, what should be done, whether it is reset to 0, the current agreement There is no clear description. Therefore, in order to prevent the NCC from inverting, the present invention defines the following processing method: If NCC+1 is the maximum value within the range of values, then NCC = NCC-1, and then through the specification defined KDF (KASME || NH) Calculate NH*, then let NH = 丽*.

Step 307: The MME sends a Handover NCC Response message to the target eNB, where the message includes {NCC, NH};

Step 308, the target eNB saves the received value of the NCC, and generates K _eNB according to the received NH value, K _eN B = KDF ( H | | PCI II EARFCN - DL);

Step 309: The target eNB returns a Handover Request Ack to the source eNB, and includes the NCC value sent by the received MME in the Handover Request Ack message.

Step 310: The source eNB sends the NCC to the UE in the Handover Command message. Step 311: After receiving the Handover Command message containing the NCC value, the UE adds the NCC value until it matches the NCC value in the Handover Command message, and then passes Safety parameter The function defined by the specification iteratively calculates the NH corresponding to the NCC, and calculates K _eNB according to the NH value, K _eNB = KDF (NH II PCI II EARFCN DL);

It should be noted that, in the present invention, it is not necessary to modify the original processing logic of the UE to generate a key, that is, the UE does not need to pay attention to how the NCC value sent by the target eNB is determined, and only needs to determine the NCC value according to the existing iterative calculation method. The NH value can be calculated by calculating K _eNB .

Step 312: The UE returns a Handover Confirm message to the target eNB.

Step 313: After completing the interaction with the handover signaling of the UE, the target eNB sends a Path Switch Request message to the MME.

Step 314: The MME sends a Path Switch Request Ack to the target eNB, where the message does not carry {NCC, ΝΗ};

Step 315: After the handover is completed, the target eNB sends a Release Resource message to the source eNB to notify the source eNB to release related resources of the UE.

As shown in the foregoing process, in step 304, the target eNB generates an NCC* according to the NCC value sent by the source eNB, and in steps 306-308, the MME determines the NH value and sends the value to the target eNB, and the target eNB according to the MME. The provided NH value generates a key, so that the source eNB cannot calculate the key K _eNB between the target eNB and the UE, and achieves one-hop forward security.

The key distribution system of the present embodiment includes: a base station and a core network, the base station includes a key information requesting unit and a key generating unit, and the core network includes a key information providing unit, wherein the key information requesting unit is configured to: Receiving the handover request requested by the terminal, requesting the key generation information from the core network;

The key information providing unit is configured to provide key generation information for the key information request unit according to the request;

The key generation unit is configured to generate a key according to the key generation information provided by the key information providing unit, and the key is used to derive a key of the access layer.

The key generation information includes an NH value corresponding to the NCC, and the key generated by the key generation unit is K _eNB ; the key information requesting unit is further configured to generate the first NCC value according to the handover request a second NCC value, and requesting key generation information from the core network by sending a handover NCC request to the core network mobility management entity, where the second NCC value is included in the handover NCC request;

The key information providing unit is further configured to determine the NH value according to the second NCC value and the locally stored NCC value as follows:

Comparing the second NCC value with the locally saved NCC value,

If the second NCC value is greater than the locally saved NCC value, the locally saved NCC value is set to the second NCC value, and the NH value corresponding to the second NCC value is calculated and determined as the NH value; if the second NCC value Less than the locally saved NCC value, the locally saved NCC value is incremented

The system further includes a terminal, and the terminal further includes a key calculation unit,

The key generation unit is configured to: generate a key according to the key generation information provided by the core network according to the request of the key information request unit, where the key is used to derive a key of an access layer . Optionally, the key generation information includes an intermediate key (NH) value corresponding to a next hop chain counter (NCC), and the key generated by the key generation unit is a K _eNB ;

The present invention also provides a terminal in a switched key distribution system, comprising a key calculation unit, the key calculation unit being arranged to be based on a next hop chain counter (NCC) sent by a base station in the switched key distribution system ) corresponding to the intermediate value calculating key (NH) value, and calculates K _eNB key based on the calculated value NH.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

One of ordinary skill in the art will appreciate that all or a portion of the above steps may be accomplished by a program instructing the associated hardware, such as a read-only memory, a magnetic disk, or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the above embodiment may be implemented in the form of hardware or in the form of a software function module. The invention is not limited to any specific form of combination of hardware and software.

Industrial Applicability The present invention provides a handover key distribution method and system. When a terminal performs handover at a source base station and a target base station, the target base station requests key generation information from the core network; the target base station generates a key according to the core network. The information generation key is used to derive the key of the access layer to solve the security problem of key distribution during the handover process. According to the key distribution scheme proposed by the present invention, the MME provides the target eNB with the generated material of the key, and the target eNB generates the K _eNB key. Thus, in the X2 handover process, even if the source eNB is compromised, the target cannot be acquired. The key K _{eNB of the eNB} solves the security problem of key distribution in the handover process and achieves the goal of 1 hop forward security.

Claims

Claim

1. A method for key distribution of a handover, comprising:

2. The method of claim 1 wherein

The key generation information includes an intermediate key (NH) value corresponding to a next hop chain counter (NCC);

In the step of the target base station generating a key according to the key generation information provided by the core network, the target base station generates the key K _eNB according to the NH value.

3. The method of claim 2, wherein

The step of the target base station requesting key generation information from the core network includes:

When receiving the handover request sent by the source base station, the target base station generates a second NCC value according to the first NCC value included in the handover request, and sends a handover NCC request to the core network mobility management entity, where the handover NCC request is performed. Include the second NCC value;

When the mobility management entity receives the handover NCC request, the NH value is determined according to the second NCC value and the locally saved NCC value, and is included in the handover NCC response and sent to the target base station.

4. The method of claim 3, wherein

The step of determining, by the mobility management entity, the NH value according to the second NCC value and the locally saved NCC value includes:

And if the second NCC value is equal to the locally saved NCC value, determining an NH value corresponding to the second NCC value as the NH value;

If the second NCC value is greater than the locally saved NCC value, the local save The NCC value is set to the second NCC value, and the NH value corresponding to the second NCC value is calculated and determined as the NH value;

If the second NCC value is less than the locally saved NCC value, the local value is saved.

5. The method according to claim 3 or 4, wherein

The switching NCC response sent by the mobility management entity to the target base station further includes an NCC value corresponding to the NH value; the target base station saves the NCC value and forwards it to the terminal;

The terminal calculates a corresponding NH value according to the NCC value sent by the target base station, and calculates the K _eNB according to the calculated NH value.

6. The method according to claim 3, wherein the target base station calculates the second NCC value according to the following formula:

NCC ₂ = fKDF(NCCi || K _eNB * || CRNTI), KDF(NCCi || K _eNB * || CRNTI)≠NCC maximum I KDF(NCCi II K _eNB * || CRNTI) -1 , KDF(NCCi || K _eNB * || CRNTI)=NCC maximum value, where NCd is the first NCC value, NCC ₂ is the second NCC value, and CRNTI is a cell radio network temporary identifier.

7. The method of claim 4, wherein

When the second NCC value is less than the NCC value saved locally by the mobility management entity, if the locally saved NCC value is incremented to be equal to the maximum value in the NCC value range, the calculation is directly performed according to the locally saved NCC value. The corresponding NH value is determined as the NH value.

8. The method according to claim 6 or 7, wherein

The value of the NCC is greater than or equal to 0 and less than or equal to 63.

A key distribution system for switching, comprising: a base station and a core network, the base station includes a key information requesting unit and a key generating unit, wherein the core network includes a key information providing unit, wherein the key The information requesting unit is configured to request key generation information from the core network when receiving the handover request requested by the terminal; The key information providing unit is configured to provide key generation information for the key information request unit according to the request;

The key generation unit is configured to generate a key based on the key generation information provided by the key information providing unit, the key being used to derive a key of an access layer.

The system of claim 9, wherein the key generation information includes an NH value corresponding to an NCC, and the key generated by the key generation unit is a K _eNB ;

The key information requesting unit is further configured to generate a second NCC value according to the first NCC value included in the handover request, and request key generation information from the core network by sending a handover NCC request to the core network mobility management entity. And including, in the handover NCC request, the second NCC value; the key information providing unit is further configured to, according to the second NCC value and the locally saved NCC value, when the handover NCC request is received The NH value is determined and included in the handover NCC response sent to the key information requesting unit.

11. The system of claim 10, wherein

The key information providing unit is further configured to determine the NH value according to the second NCC value and the locally saved NCC value as follows:

Comparing the second NCC value with the locally stored NCC value,

And if the second NCC value is greater than the locally saved NCC value, setting the locally saved NCC value to the second NCC value, calculating an NH value corresponding to the second NCC value, and determining The NH value;

12. The system of claim 10 or 11, further comprising a terminal, the terminal being configured to include a key calculation unit,

The key information providing unit is further configured to send the message to the key information requesting unit The key information requesting unit is further configured to save after receiving the NCC value, and forward the same to the terminal;

The key calculation unit is configured to calculate a corresponding NH value according to the received NCC value sent by the key information request unit, and calculate K _eNB according to the calculated NH value.

13. A base station in a switched key distribution system, comprising a key information requesting unit and a key generating unit, wherein:

The key generation unit is configured to: generate a key according to the key generation information provided by the core network according to the request of the key information request unit, where the key is used to derive a key of an access layer .

The base station according to claim 13, wherein the key generation information includes an intermediate key (NH) value corresponding to a next hop chain counter (NCC), and the key generated by the key generation unit is

K _e B;

15. A terminal in a switched key distribution system, comprising a key calculation unit, the key calculation unit being arranged to receive a next hop chain counter (NCC) value according to a base station in the switched key distribution system Calculate the corresponding intermediate key (NH) value and calculate the key based on the calculated NH value